Generally, a passenger in a passenger vehicle, such as an automobile, airplane, bus or train, suffers significant neck strain when resting since seats in such passenger vehicles typically provide support only to the back portion of the passenger's head. More specifically, since seats in such passenger vehicles are not designed to keep the passenger's head in a substantially upright, vertical orientation relative to the passenger's torso (e.g., when the passenger is at rest or sleeping), neck strain may result due to the natural instability of an unsupported head when no muscles are being used to support the head.
In order to alleviate such neck strain, various devices have been developed. For instance, pillows designed to fit around the backside of the passenger's neck have been developed. Such neck pillows are inflatable with air or consist solely of a foam material. However, such neck pillows generally do not provide adequate support to inhibit neck strain due to their readily deformable or "sponge-like" nature. Further, use of such neck pillows tends to allow the entire body of the user to slide sideward because lateral acceleration causes the passenger's body to slip against the seat. In addition, such neck pillows typically do not allow passengers to adjust the configuration of the device to suit the passenger's tastes or dimensions.